This invention pertains to a burn-in apparatus for isolating faulty semiconductor chips and more particularly to an improvement thereof for ensuring proper operation of the burn-in apparatus. More specifically, the invention relates to monitoring electrical signals which exercise the semiconductor chips to verify that clock-driver circuits generating the electrical signals and electrical connections between the clock-driver circuits and the semiconductor chips are functioning correctly.
Burn-in apparatus is known in which the DIPs (dual in-line packages) or the DUTs (devices under test) are placed in PC (printed circuit) boards, called burn-in boards (BIBs), that are then plugged into the front side of a mother board in a panel (back plane) forming the back part of the hollow back wall of an oven (burn-in chamber) where controlled temperature is maintained. A plurality of clock boards, each clock board to be connected to, e.g., a plurality of burn-in boards, are plugged into the back side of the mother board at the back of the panel, it being desirable to have the clock boards as close to the burn-in boards as possible to reduce electrical interference and signal degredation.
Heretofore, the clock-driver signals have been monitored by comparing the output signals of each driver output line with its input line from the clock. This procedure adequately protects against clock-driver circuit failure but does not detect a failed electrical connection between the clock-driver circuit and the burn-in boards. In order to detect failure in the electrical connections, e.g., including card-edge connectors or other quick connectable and disconnectable connectors, between several burn-in boards and the back side of the mother board in the back plane, as well as connectors at the front side thereof which connect the clock boards to the mother board, it is necessary that the clock-driver signals be monitored on each burn-in board, and all these monitor lines must then be connected back through the back panel via further quick connectable and disconnectable connectors to the monitoring detector apparatus outside the burn-in chamber. The additional connections and detector apparatus necessary to accomplish such burn-in board monitoring renders the procedure prohibitively expensive. Hence, the present apparatus and method for exercising semiconductor chips does not provide a reasonable means for assuring that all semiconductor chips are indeed being exercised.